Up to date, it is well known that encoder processing devices, storing memory by previously calculating a position detection error generated by an offset voltage, an amplitude error, a wave distortion, and the like which are characteristics of two-phase analog signals obtained from a sensor signal detecting section, and correcting the position detection signal on the basis of the detection error data in the process of an usual position detection (For example, refer to patent document 1).
FIG. 12 is a block diagram illustrating a configuration of the known encoder processing device.
In FIG. 12, 51 indicates an analog amplifier amplifying two-phase analog signals Sa and Sb which are obtained from a sensor signal detecting section. 52 indicates an analog-digital converter converting the amplified two-phase analog signals to digital signals. 53 indicates a digital interpolation circuit converting the converted two-phase digital signals to position data. 54 indicates a detection error data calculator receiving the position data from the digital interpolation circuit 53 and calculating detection error data for the correction. 55 indicates a detection error correction circuit correcting detection error of the position data by the use of the detection error data for the correction and including a detection error storing register 551 for the correction and a correction calculator 552. 56 indicates a position data generator generating the position data which has a plurality of cycles from the corrected position data in one cycle and the number of cycles of an original signal.
It will be described about an operation of the known device in the next.
First, methods of an error data calculation and storage thereof will be described. Objects which are targets for a measurement and not illustrated are moved at a constant velocity. The two-phase analog signals Sa and Sb which can be obtained from the sensor signal detecting section are amplified by the analog amplifier 51 and are converted into digital data by analog-digital converter 52. Then, the signals are converted into the position data by the digital interpolation circuit 53.
Two objects are moved at the constant velocity, and the movement distance of the one cycle is previously measured. Accordingly, by sampling the distance in the one cycle at equal intervals, the movement distance can be calculated in each sampling process. The detection error data calculator 54 calculates the position error from ideal position data which is obtained by the calculation and the position data which is detected in the process of the sampling. The calculator stores the position error data in the detection error storing register 551 for the correction in the detection error correction circuit 55.
Second, it will be described about a method correcting the position data by using the stored position error data. In the usual process of detecting the position, the position data is calculated on the basis of the two-phase analog signals which can be obtained from the sensor signal detecting section. Then, the correction calculator 552 corrects the detection error of the position data by the use of the detection error data which is stored in the detection error storing register 551 for the correction. As a result, the calculator gives an output to the position data generator 56.
As mentioned above, the known encoder signal processing devices store the position error data corresponding to the detection position in the detection error storing register for the correction. The known devices also correct the detection error of the position data by the use of the position error data.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-254785 (refer to page 10 and FIG. 2)